Abstract

We show that the Higgs portal interactions involving extra dark Higgs field can save generically the original Higgs inflation of the standard model (SM) from the problem of a deep non-SM vacuum in the SM Higgs potential. Specifically, we show that such interactions disconnect the top quark pole mass from inflationary observables and allow multi-dimensional parameter space to save the Higgs inflation, thanks to the additional parameters (the dark Higgs boson mass m {sub φ}, the mixing angle α between the SM Higgs H and dark Higgs Φ, and the mixed quartic coupling) affecting RG-running of the Higgs quartic coupling. The effect of Higgs portal interactions may lead to a larger tensor-to-scalar ratio, 0.08 ∼< r ∼< 0.1, by adjusting relevant parameters in wide ranges of α and m {sub φ}, some region of which can be probed at future colliders. Performing a numerical analysis we find an allowed region of parameters, matching the latest Planck data.

In cosmic inflation driven by a scalar gauge singlet field with a tree level Higgs potential, the scalar to tensor ratio r is estimated to be larger than 0.036, provided the scalar spectral index n{sub s{>=}}0.96. We discuss quantum smearing of these predictions arising from the inflaton couplings to other particles such as grand unified theory scalars, and show that these corrections can significantly decrease r. However, for n{sub s{>=}}0.96, we obtain r{>=}0.02 which can be tested by the Planck satellite.

A sizeable tensor-to-scalar ratio, such as recently claimed by BICEP2, would imply a scale of inflation at the typical scale of supersymmetric grand unification. This could be an accident, or strong support for supersymmetric theories. Models of F-term hybrid inflation naturally connect the GUT scale with the inflationary scale, but they also predict the tensor-to-scalar ratio to be unmeasurably small. In this work we analyze a general UV embedding of F-term hybrid inflation into a supergravity theory with a general Kähler potential. The CMB observables are generated during the early phase of inflation, at large inflaton values, where the potentialmore » is dominated by Planck-suppressed operators. Tuning the leading higher-order terms can give an inflaton potential with sizeable tensor fluctuations and a field excursion which is still sub-Planckian but close to the Planck scale, as expected from the Lyth bound.« less

We study the single field slow-roll inflation models that better agree with the available CMB and LSS data including the three years WMAP data: new inflation and hybrid inflation. We study these models as effective field theories in the Ginsburg-Landau context: a trinomial potential turns out to be a simple and well motivated model. The spectral index n{sub s} of the adiabatic fluctuations, the ratio r of tensor to scalar fluctuations and the running index dn{sub s}/dlnk are studied in detail. We derive explicit formulas for n{sub s}, r and dn{sub s}/dlnk and provide relevant plots. In new inflation, andmore » for the chosen central value n{sub s}=0.95, we predict 0.03<r<0.04 and -0.000 70<dn{sub s}/dlnk<-0.000 55. In hybrid inflation, and for n{sub s}=0.95, we predict r{approx_equal}0.2 and dn{sub s}/dlnk{approx_equal}-0.001. Interestingly enough, we find that in new inflation n{sub s} is bounded from above by n{sub smax}=0.961 528... and that r is a two valued function of n{sub s} in the interval 0.96<n{sub s}<n{sub smax}. In the first branch we find r<r{sub max}=0.114 769.... In hybrid inflation we find a critical value {mu}{sub 0crit}{sup 2} for the mass parameter {mu}{sub 0}{sup 2} of the field {sigma} coupled to the inflaton. For {mu}{sub 0}{sup 2}<{lambda}{sub 0}M{sub Pl}{sup 2}/192, where {lambda}{sub 0} is the cosmological constant, hybrid inflation yields a blue tilted n{sub s}>1 behavior. Hybrid inflation for {mu}{sub 0}{sup 2}>{lambda}{sub 0}M{sub Pl}{sup 2}/192 fulfills all the present CMB+LSS data for a large enough initial inflaton amplitude. Even if chaotic inflation predicts n{sub s} values compatible with the data, chaotic inflation is disfavored since it predicts a too high value r{approx_equal}0.27 for the ratio of tensor to scalar fluctuations. The model which best agrees with the current data and which best prepares the way to the expected data r(less-or-similar sign)0.1, is the trinomial potential with negative mass term: new inflation.« less

Recently, we have shown that scalar spectra with lower power on large scales and certain other features naturally occur in punctuated inflation, i.e. the scenario wherein a brief period of rapid roll is sandwiched between two stages of slow roll inflation. Such spectra gain importance due to the fact that they can lead to a better fit of the observed CMB anisotropies, when compared to the conventional, featureless, power law spectrum. In this paper, with examples from the canonical scalar field as well as the tachyonic models, we illustrate that, in punctuated inflation, a drop in the scalar power onmore » large scales is always accompanied by a rise in the tensor power and, hence, an even more pronounced increase in the tensor-to-scalar ratio r on these scales. Interestingly, we find that r actually exceeds well beyond unity over a small range of scales. To our knowledge, this work presents for the first time, examples of single scalar field inflationary models wherein r>>1. This feature opens up interesting possibilities. For instance, we show that the rise in r on large scales translates to a rapid increase in the angular power spectrum, C{sub l}{sup BB}, of the B-mode polarization of the CMB at the low multipoles. We discuss the observational implications of these results.« less

We reconsider nonminimal {lambda}{phi}{sup 4} chaotic inflation which includes the gravitational coupling term {xi}R{phi}{sup 2}, where {phi} denotes a gauge singlet inflaton field and R is the Ricci scalar. For {xi}>>1, we require, following recent discussions, that the energy scale {lambda}{sup 1/4}m{sub P}/{radical}({xi}) for inflation should not exceed the effective UV cutoff scale m{sub P}/{xi}, where m{sub P} denotes the reduced Planck scale. The predictions for the tensor-to-scalar ratio r and the scalar spectral index n{sub s} are found to lie within the Wilkinson Microwave Anisotropy Probe 1-{sigma} bounds for 10{sup -12} < or approx. {lambda} < or approx. 10{supmore » -4} and 10{sup -3} < or approx. {xi} < or approx. 10{sup 2}. In contrast, the corresponding predictions of minimal {lambda}{phi}{sup 4} chaotic inflation lie outside the Wilkinson Microwave Anisotropy Probe 2-{sigma} bounds. We also find that r > or approx. 0.002, provided the scalar spectral index n{sub s{>=}}0.96. In estimating the lower bound on r, we take into account possible modifications due to quantum corrections of the tree level inflationary potential.« less